Government regulations in various jurisdictions make it necessary to limit the maximum speed obtainable by motor vehicles, particularly motorcycles with small, two-stroke engines.
One conventional approach to limiting the speed of motorcycles with carburetor equipped engines achieves a power reduction and thus a speed limitation by adjusting the fuel-air mixture so that it is too rich above a predetermined speed. This approach suffers from a number of disadvantages, however. A principle disadvantage is that gasoline consumption and pollution emissions are increased at high rotational speeds. Further, engines so tuned do not operate in a optimum power range at low rotational speeds since the starting torque is relatively low. Another serious disadvantage is that the tuning of such engines can be relatively easily changed to increase the limiting speed.
Another conventional approach to limiting the speed of motorcycles entails interrupting the ignition when a predetermined rotational speed is reached. In addition to achieving only a rotational engine speed limitation, and not actually a vehicle speed limitation, this approach suffers from the fact that it involves a jerky reduction in speed due to misfiring, and thus impairs the safety of the driver.